Hearing aid



FIG. 1 is a reduced perspective view of a hearing aid, showing the design with an attached flexible ear tube;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a back end view thereof; and,

FIG. 7 is a front end view thereof.

The features shown in broken lines represent environment and do not form part of the claimed design. 

I claim the ornamental design for a hearing aid, as shown and described. 